We've moved from a mailing list which was a black-hole for Content with very poor discoverability, and despite having many members was mostly read-only/ignored with just the same small group responding. We're now directing future support questions to StackOverflow. Many people were using GitHub issues to communicate, but this was primarily only seen by the Core team and effectively invisible to the wider community.

We see much more engaging and visible feedback on G+, people frequently comment on posts, +1 and re-share.